1. Field of the Invention
This invention relates to wireless communications, and more particularly to reducing interference in wireless communications.
2. Description of the Related Art
Currently, there are licensed wireless communication bands and unlicensed communication bands existing. In some schemes, the licensed and unlicensed bands are very close to each other. For example, the licensed 2.3 GHz band and the unlicensed 2.4 GHz (IEEE 802.11 based Wi-Fi) bands are very close to each other and might cause interference with each other, especially if operating in close proximity to each other. Consider a device capable of communicating using both a Broadband Wireless Access (BWA) technology such as Long Term Evolution (LTE) or IEEE Worldwide Interoperability for Microwave Access (WiMAX) and Wi-Fi, the signals may interfere with each other if both the above mentioned communications modes happen simultaneously. Similarly, if there are two devices in close proximity, where one of the devices is capable of communicating using Wi-Fi and the second device is capable of communicating using a BWA technology, the signals may interfere with each other if both the devices attempt to communicate simultaneously. Interference between signals may lead to loss in signal quality and subsequent loss of data.
Existing solutions may use a more robust modulation or coding scheme for the licensed bands to reduce self-interference. However, this approach results in a drop in capacity of the overall system.
Another existing solution makes use of filters to filter out the interfering signal. However, filters may not be effective in combating interference, when there is no guard band present in the communication bands. Further, addition of filters may results in an increase in cost of the devices.
The current 802.16 draft specification includes an interference mitigation scheme between communication radios present within a single device. The draft specification assumes that the communications radios can communicate with each other using OS controlled hardware signaling and hence are able to perform time division multiplexing of the communication signals over the shared communication channel.
Other solutions also talk about mitigating interference between communication radios present within a single device. The solution makes use of a control signal transmitted over the air by the interfering radio to back off its own transmissions for a time period specified in the control signal. However, the primary disadvantage is that the control signal which is transmitted over the air may inhibit communications to be carried out by other devices present within the vicinity, causing widespread disruption for an entire non-interfering network.